1. Field of the Invention
This invention relates to a substrate processing apparatus and a substrate processing method for processing substrates. Examples of substrates to be processed include semiconductor wafers, substrates for liquid crystal displays, substrates for plasma displays, substrates for FEDs (Field Emission Displays), substrates for optical disks, substrates for magnetic disks, substrates for magneto-optical disks, substrates for photomasks, ceramic substrates, and substrates for solar cells.
2. Description of Related Art
A substrate, such as a semiconductor wafer or a glass substrate for a liquid crystal display device, is processed by use of a processing liquid in a production process in which a semiconductor device, a liquid crystal display device, or the like is produced.
For example, Japanese Published Unexamined Patent Application No. 2007-318016 discloses a substrate processing apparatus of the single-substrate processing type that performs bevel etching. This substrate processing apparatus includes a spin chuck that horizontally holds and rotates a substrate around a vertical axis and a lower-surface nozzle that faces the central portion of a lower surface of the substrate held by the spin chuck. A chemical solution discharged from the lower-surface nozzle is supplied to the central portion of the lower surface of the substrate being rotated. Thereafter, the chemical solution supplied thereto spreads outwardly along the lower surface of the substrate by the rotation of the substrate, and turns to the peripheral portion of an upper surface of the substrate while proceeding along the peripheral end surface of the substrate. As a result, the chemical solution is supplied to the whole area of the peripheral portion of the upper surface of the substrate.
Likewise, Japanese Published Unexamined Patent Application No. 2007-142077 discloses a substrate processing apparatus of the single-substrate processing type that performs bevel etching. This substrate processing apparatus includes a spin chuck that horizontally holds and rotates a substrate around a vertical axis and a peripheral-portion processing nozzle that faces the peripheral portion of an upper surface of the substrate held by the spin chuck. A chemical solution discharged from the peripheral-portion processing nozzle is supplied to the peripheral portion of the upper surface of the substrate being rotated. As a result, the chemical solution is supplied to the whole area of the peripheral portion of the upper surface of the substrate.
Additionally, U.S. Patent Application Publication No. 2006/0151008 A1 discloses a cleaning method for cleaning a substrate by use of a highly viscous liquid. In this cleaning method, a highly viscous liquid is supplied to an upper surface of a substrate. Thereafter, the substrate starts being rotated. The liquid supplied thereto moves outwardly on the substrate by the rotation of the substrate. As a result, the highly viscous liquid is discharged from the substrate. Foreign matters adhering to the upper surface of the substrate are discharged from the substrate along with the highly viscous liquid. As a result, the foreign matters are removed from the substrate.
In the substrate processing apparatuses of Japanese Published Unexamined Patent Application Nos. 2007-318016 and 2007-142077, a chemical solution supplied to the peripheral portion of the upper surface of the substrate is discharged outwardly by the rotation of the substrate. Therefore, the chemical solution is required to be discharged from the nozzle during the processing of the substrate by use of the chemical solution. Therefore, a state in which the peripheral portion of the upper surface of the substrate and the chemical solution are in contact with each other is maintained, and the chemical solution that has a sufficient processing capability continues being supplied to the peripheral portion of the upper surface of the substrate. However, the consumption of the chemical solution will be increased if the chemical solution continues being discharged from the nozzle.
On the other hand, in the cleaning method of U.S. Patent Application Publication No. 2006/0151008 A1, a highly viscous liquid is supplied to an upper surface of a substrate. The liquid is high in viscosity, and hence can be held on the substrate. Therefore, a state in which the substrate and the liquid are in contact with each other can be maintained even if a highly viscous liquid does not continue being supplied to the substrate. Therefore, the consumption of the liquid can be reduced. However, in this cleaning method, foreign matters cannot be sometimes removed from the substrate if adhesion of the foreign matters to the upper surface of the substrate is extremely firm.
In order to reduce the consumption of a chemical solution and to reliably remove foreign matters from a substrate, it is possible to, for example, employ a method for supplying the substrate with a highly viscous chemical solution capable of dissolving the substrate. According to this method, the substrate can be allowed to hold the chemical solution because the chemical solution has high viscosity. Therefore, the consumption of the chemical solution can be reduced. Additionally, foreign matters adhering to the substrate can be lifted off from the substrate along with a portion of the substrate by allowing the substrate and the chemical solution to react together and hence dissolving the portion of the substrate. Therefore, the foreign matters can be reliably removed from the substrate.
However, in this method, the chemical solution contiguous to the substrate is not replaced by a new chemical solution, and therefore there is a case in which much time is consumed to allow the substrate and the chemical solution to sufficiently react together, and hence a satisfactory processing speed cannot be secured. It is conceivable that the substrate is located at that place (i.e., the position to which the chemical solution has been supplied) until the substrate and the chemical solution sufficiently react together, and, if so, a highly viscous chemical solution cannot be supplied to a subsequent substrate until the substrate to which the chemical solution has been supplied is taken out. Therefore, throughput (i.e., the number of substrates processed per unit time) will be decreased.
It is therefore an object of the present invention to provide a substrate processing apparatus and a substrate processing method that are capable of reducing the consumption of a chemical solution and capable of restraining or preventing a decrease in throughput.